diff options
| author | Jann Horn <jannh@google.com> | 2019-02-27 21:29:52 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2019-05-02 21:42:01 +0100 |
| commit | c90030281dc8b6a25ac8850e98e15877f80b8d66 (patch) | |
| tree | 53cc3d855108d1647e30659883729e8c221e78aa | |
| parent | 120d66394f05ec50a018168850a8db6518ea2d9b (diff) | |
mm: enforce min addr even if capable() in expand_downwards()
commit 0a1d52994d440e21def1c2174932410b4f2a98a1 upstream.
security_mmap_addr() does a capability check with current_cred(), but
we can reach this code from contexts like a VFS write handler where
current_cred() must not be used.
This can be abused on systems without SMAP to make NULL pointer
dereferences exploitable again.
Fixes: 8869477a49c3 ("security: protect from stack expansion into low vm addresses")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | mm/mmap.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 328acb37e23d..775c7723fd5e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2244,12 +2244,11 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address) { struct vm_area_struct *prev; - int error; + int error = 0; address &= PAGE_MASK; - error = security_mmap_addr(address); - if (error) - return error; + if (address < mmap_min_addr) + return -EPERM; /* Enforce stack_guard_gap */ prev = vma->vm_prev; |